A primary key having two or more attributes is called composite key. It is a combination of two or more columns.
An example can be −
Here our composite key is OrderID and ProductID −
| {OrderID, ProductID} |
Let us see another example −
<Student>
| StudentID | StudentEnrollNo | StudentMarks | StudentPercentage |
| S001 | 0721722 | 570 | 90 |
| S002 | 0721790 | 490 | 80 |
| S003 | 0721766 | 440 | 86 |
Above, our composite keys are StudentID and StudentEnrollNo. The table has two attributes as primary key.
Therefore, the Primary Key consisting of two or more attribute is called Composite Key.